script.js

const inputBox = document.getElementById("input-box");
const listContainer = document.getElementById("list-container");

function addTask(){
    if (inputBox.value === '') {
        alert("You Must Write Something");
    }
    else {
        let li = document.createElement("li");
        li.innerHTML = inputBox.value;
        listContainer.appendChild(li);
        let span = document.createElement("span");
        span.innerHTML = "\u00d7";
        li.appendChild(span);
    }
    inputBox.value = '';
    saveData()
}

listContainer.addEventListener("click", function(e) {
if (e.target.tagName === "LI") {
    e.target.classList.toggle("checked");
    saveData()
}
else if (e.target.tagName === "SPAN") {
    e.target.parentElement.remove();
    saveData()
}
},false)

function saveData() {
    localStorage.setItem("data", listContainer.innerHTML);
}

function showData() {
    listContainer.innerHTML = localStorage.getItem("data");
}
showData()